STOCK PLANS AND STOCK BASED COMPENSATION - Restricted Stock Awards (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Shares
Granted (in shares)	0	8,204		0
Additional disclosures
Compensation expense	$ 70			$ 103			$ 241	$ 282
Restricted stock
Shares
Nonvested at the beginning of the period (in shares)			104,319				104,319
Granted (in shares)							30,302
Vested (in shares)							(28,432)
Forfeited (in shares)							(1,250)
Nonvested at the end of the period (in shares)	104,939						104,939
Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)			$ 20.03				$ 20.03
Granted (in dollars per share)							34.38
Vested (in dollars per share)							16.31
Forfeited (in dollars per share)							23.62
Nonvested at the end of the period (in dollars per share)	$ 25.14						$ 25.14
Restricted stock | 2015 Plan
Additional disclosures
Unrecognized compensation costs	$ 1,553						$ 1,553
Weighted-average period of expected recognition of the cost							2 years 2 months 12 days
Compensation expense	$ 175			$ 160			$ 588	$ 512
Restricted stock | Executive officer and other employees
Stock-based compensation
Vesting percentage of stock awards on third anniversary of grant date	100.00%						100.00%
Shares
Granted (in shares)		13,500	12,802		16,000
Weighted Average Grant Date Fair Value
Granted (in dollars per share)			$ 34.99
Common Stock | Executive officer and other employees
Shares
Granted (in shares)	4,000					24,152
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 34.82	$ 33.68			$ 22.47	$ 21.47